How to check for bash shell syntax errors in practice?

Question

I need to check whether a set of scripts are syntactically correct. I know there are couple of posts around suggesting to use bash -n <script_name> but I run this and I get nothing out e.g.

good.sh

#!/bin/bash

echo "hello"

bad.sh

#!/bin1/bash1

eco "hello"

If I do:

$ bash -n bad.sh; echo $?
0
$ bash -n good.sh; echo $?
0

So how do you discriminate between good and bad exactly?

As far as bash knows, there may be a command by the name of `eco`, so this isn't really a syntax error. — Tom Fenech, Nov 27 '14 at 14:47
OK I see. If you answer and put a bad example I will accept. Thank you. — SkyWalker, Nov 27 '14 at 14:50
possible dup:http://stackoverflow.com/questions/171924/how-do-i-check-syntax-in-bash-without-running-the-script — Jason Hu, Nov 27 '14 at 14:50
I know there are others but they are not specific enough probably. — SkyWalker, Nov 27 '14 at 14:50
dvd818 showed that there is a website you can use: http://www.shellcheck.net — Jason Hu, Nov 27 '14 at 14:51
I know I saw it before but it doesn't show a bad case, so you run it with multiple possible errors and they all come back ok — SkyWalker, Nov 27 '14 at 14:52

score 2 · Accepted Answer · answered Nov 27 '14 at 15:22

bash -n checks whether Bash can parse the code (that is, the syntax is correct), not whether the code is "correct." "Correct" can have a lot of meanings, most of which programs will never be able to verify:

Can be parsed (bash -n).
Finishes without error (if ./script.sh; then [...]; fi).
Prints something which follows a specific format.
Prints something useful.
Any of the above within a specific environment, for example one which has a shell interpreter that lives in /bin1/bash1 and a command eco which shows you the most ecologically friendly beer bottles available within a 5 parsec radius.

It's too bad the `-e` option can't be overloaded with `-n` to indicate something like "check if command is available" (and continue to test for syntax errors). — shellter, Nov 27 '14 at 16:27

How to check for bash shell syntax errors in practice?

1 Answers1